Coupon Configuration Problems

I created a Coupon choosing coupon in options. The problem i have is that i want to send this coupon to a client and then he has to input it on the coupon field, but when i create the coupon and surf the web anononymously, choose one product and go to checkout, the coupon is already there, it says your coupon is (coupon_name) and it is fixed there, and if i press the eliminate coupon button, nothing happens.

that was it thank you